The present invention relates to telescoping slide assemblies, and particularly to a slide assembly having three slide members and lock mechanisms for locking the slide members in various retracted and extended positions. More particularly, the present invention relates to a telescoping slide assembly that contains automatic release mechanisms for controlling unlocking of the slide members during telescoping movement of the slide members between extended and retracted positions.
A conventional telescoping slide assembly typically includes a stationary slide member, a load-carrying slide member, and an intermediate slide member. The intermediate slide member is positioned and configured to move the load-carrying slide member toward and away from the stationary slide member. Typically, a pair of telescoping slide assemblies are positioned in side-by-side spaced-apart parallel relation so that either a load-carrying platform or one or more pieces of equipment can be carried on the two side-by-side load-carrying slide members. It is also common to use a pair of telescoping slide assemblies to support a cabinet drawer between a retracted position inside the cabinet and an extended position outside the cabinet.
The stationary slide member is typically mounted to a fixed frame to anchor the slide assembly. The frame could be a cabinet, a truck bed, or any other suitable platform. For example, it is known to use telescoping slide assemblies to slide heavy pieces of equipment into and out of a truck bed.
Various kinds of equipment or loads can be anchored to the movable load-carrying slide members so that such loads can be moved easily relative to the truck bed or the like during telescoping extension and retraction of the intermediate and load-carrying slide members in each slide assembly relative to the stationary slide members that are anchored to the truck bed. Typically, a telescoping slide assembly is extended and retracted manually by an operator and thus must be capable of moving heavy loads easily and quickly under the control of an operator during loading of equipment onto the truck and unloading of equipment from the truck.
It is known to provide locking interconnections between each of the three slide members so that extension or retraction of the slide members relative to each other can be prevented. This allows a drawer or equipment rack mounted on a pair of telescoping slide assemblies to be extended outward in the extending direction and locked to maintain a desired extended position. Since these locking interconnections must generally be manually engaged and disengaged, separate manual unlocking actions are required before such a drawer or equipment can be extended. The use of a locking mechanism to prevent relative movement of two sliding tracks until manual release of the locking mechanism is known. See, for example, U.S. Pat. No. 4,200,342 to Fall.
Typically, as the telescoping slide assemblies extend to move the equipment or load from the retracted position, the slide members lock automatically in a partly extended position. An operator initiates the extension process by manually actuating a release mechanism to allow the slide members to extend relative to one another. However, friction between the load-carrying slide member and the intermediate slide member will sometimes cause these two slide members to "stick" together and therefore move together as a unit relative to the stationary slide member toward an extended position. In some instances, the operator will have let go of the release mechanism prematurely and therefore will not have actuated the release mechanism fully to unlock the load-carrying slide member so that it is free to move relative to the intermediate slide member. In such a circumstance, when the intermediate slide member reaches its fully extended position and is locked to the stationary slide member, the load-carrying slide member is still locked to the now immobile intermediate slide member and the slide assembly is stopped prematurely in a partly extended position.
In order to continue moving the load to the fully extended position, the operator must manually actuate the release mechanism a second time to allow the load-carrying slide member to extend to its fully extended position relative to the fixed intermediate slide member. In many applications, the need for a second manual actuation of the release mechanism is a nuisance. This problem is especially aggravating in cases wherein an operator is using the telescoping slide assembly to move a heavy unit and must manually actuate the release mechanism twice to move the slide members in the slide assembly to their fully extended positions. Therefore, telescoping slide assemblies that provide a release mechanism for allowing the slide members to fully extend without stopping at a partly extended position would be an improvement over conventional slide assemblies.
Another problem facing some users of telescoping slide assemblies is inadvertent damage to a locking pin in the release mechanism during movement of the load-carrying and intermediate slide members relative to the stationary slide member toward their fully retracted positions. Such damage can sometimes occur if the operator pushes the load-carrying and intermediate slide members toward their fully retracted positions without realizing that those two slide members are still locked together to move as a unit. This problem is known to happen when the operator has the slide assembly open for servicing a unit but did not need to extend the slide assembly to its fully extended position to gain access to that part of the unit needing repair or attention.
Unless the operator realizes that the load-carrying and intermediate slide members are locked together as they are moved toward their fully retracted positions and then manually actuates the release mechanism at the proper time to enable the load-carrying slide member to continue moving toward its fully retracted position once the intermediate slide member reaches its fully retracted position, it is possible that the locking pin in the release mechanism will be urged by the load-carrying slide member to strike sharply against the intermediate slide causing the locking pin to break or deform, thus disabling the release mechanism. What is needed is a mechanism for automatically unlocking the load-carrying and intermediate slide members as they move toward fully retracted positions under the circumstances just described to prevent unwanted damage to the locking pin.
According to the present invention, a telescoping slide assembly is provided for moving a load between a fully retracted position and a fully extended position. The telescoping slide assembly includes a load-carrying slide member and an intermediate slide member and each slide member is formed to include a locking aperture. The telescoping slide assembly further includes means for locking the load-carrying and intermediate slide members to their fully retracted positions. The locking means includes a locking pin and means for yieldably biasing the locking pin to a slide-locking position passing through the locking aperture of each slide member when the slide members occupy their fully retracted positions.
The telescoping slide assembly also includes actuator means for withdrawing the locking pin from either the locking aperture in the stationary slide member or the locking apertures in both of the intermediate and stationary slide members to allow an operator to move the intermediate and load-carrying slide members toward their fully extended positions. Ramp means is provided in the locking aperture formed in the intermediate slide member for automatically camming a locking pin passing through only the locking apertures formed in the load-carrying and stationary slide members to a raised position out of the locking aperture formed in the intermediate slide member without operating the actuator means so that the load-carrying slide member is free to move relative to the intermediate slide member toward its fully extended position.
In preferred embodiments, a first bushing is mounted in the locking aperture formed in the intermediate slide member and that first bushing provides the ramp means. Illustratively, the first bushing includes an aperture receiving the locking pin and a conical locking pin-ramping surface communicating with the aperture and facing toward the load-carrying slide member.
To extend the telescoping slide assembly, the operator first uses the actuator means to withdraw the locking pin from the locking aperture formed in the stationary slide member and then moves the load-carrying slide member toward its fully extended position. During such movement, the locking pin will engage the conical surface in the first bushing and be ramped automatically to a raised position disengaging the locking aperture formed in the intermediate slide member. Now, the load-carrying slide member is unlocked from the intermediate slide member and is free to move to its fully extended position.
Illustratively, the intermediate slide member is also formed to include a second locking aperture near the outermost end of the intermediate slide member and a second bushing is mounted in this second locking aperture. This second bushing is configured to cam the locking pin out of the second locking aperture during certain operating conditions to prevent breakage or deformation of the locking pin.
The second bushing includes another aperture for receiving the locking pin and a conical locking pin-camming surface communicating with the aperture and facing toward the load-carrying slide member. The locking pin will, in certain circumstances, engage the conical surface in the second bushing and be cammed automatically to a raised position disengaging the second locking aperture formed in the intermediate slide member as the load-carrying slide moves toward its retracted position.
The camming action taking place in the second bushing protects the locking pin from being broken or deformed during retraction of the slide assembly in the event that the operator fails to lift the locking pin manually to its raised position using the actuator means at the start of a slide-retracting sequence. As noted above, this circumstance might occur in the event that an operator does not need to operate the actuator mechanism and raise the locking pin to unlock the locked connection between the load-carrying and intermediate slide member to begin the slide-retracting sequence because the slide assembly was not previously pulled to its fully extended position wherein the intermediate slide member would have been locked to the stationary slide member and the load-carrying slide member would have been locked to the intermediate slide member. Thus, the cam means in the second bushing functions to protect the locking pin in circumstances where a slide-retracting sequence begins and the intermediate slide member is not locked to the stationary slide member but is locked to the load-carrying slide member.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.